FR2475929A1 - DIFFUSER-MIXER INSTALLATION ELEMENT, AND METHOD FOR PERFORMING AND INTENSIFYING THE PROCESSES OF TRANSFER OF HEAT AND / OR MATERIAL BETWEEN LIQUID-LIQUID PHASES AS WELL AS LIQUID-SOLID PHASES - Google Patents

Abstract

The process according to the invention and the mixing diffuser employed to carry it out make it possible to effect heat transfer and/or mass transfer processes between liquid-liquid and liquid-solid phases while employing a conventional autoclave as the base system. During the process, the mutual intensive contact and intimate mixing of the substances involved is effected by an insertion element inserted in the autoclave, intensive heat transfer being achieved with a freely selectable and dimensionable external cooler. The beneficial effects of the process and of the insertion element, as well as the intensive heat exchange are caused by the circulation of the portion of the liquid phase.

Description

 Installation element, diffuser-mixer, and method for carrying out and intensifying the heat and / or material transfer processes between liquid-liquid phases as well as between liquid-solid phases.

 The present invention relates to an installation element, a diffuser-mixer, and a method for carrying out and intensifying the heat and / or material transfer processes between liquid-liquid phases as well as between liquid-solid phases.

 The method and the installation element in accordance with the present invention allow the process of heat and / or material transfer to be carried out intensively between liquid-liquid phases as well as between liquid-solid phases using an autoclave. conventionally used, which serves as the basic device. In the process, the intensive mutual contact and the mixing effect are obtained by means of an internal accessory element having a particular action introduced into the autoclave, and the intensive heat transfer is obtained by means of '' an external refrigerant which can be freely chosen and dimensioned.The process ensures the favorable effects of the internal accessory element and the achievement of an intensive supply or elimination of heat by circulating an appropriate part of the phase liquid with appropriate speed.

In chemical industry technology, the following heat and material transfer processes between liquid-liquid phases or between liquid-solid phases are most often used to
- dissolution, extraction,
- chemical reactions in a liquid phase
homogeneous or heterogeneous,
- the separation of a solid material from a
solution, crystallization, precipitation, salting out,
- in addition the formation of suspensions and emulsions.

 In current industrial practice, these operations, with the exception of a few special cases, are carried out in autoclaves, mixing containers provided with a heating and cooling jacket.

 If indeed, in the previous decades, important new intensive processes have been known, such as for example the processes using flu1; #disation, rotary film, foam columns and geysers, their use on an industrial scale n was just a sporadic phenomenon.

One of the explanations for this is that neither the manufacturers of chemicals, nor the manufacturers of related industries were able to shoulder the considerable multiple expenses which were necessary to modernize an already existing installation. The current processes require in particular installations working continuously, also the expensive transformation, requiring investments for their operation, present installations generally based on a discontinuous technology was essential.

 If indeed the manufacturers recognized the advantages of the current intensive process, i.e. high specific capacity, uniform product quality, etc., the producers could not shoulder the prices and the risks entailed by the introduction of A new process as long as any facility, even using a theoretically old process, could still function from the point of view of economic profitability. In particular, such a step, for which energy problems and economic difficulties are manifested worldwide, requires reflection.

 On the other hand, the increase in productivity and the improvement of the quality of the products from the point of view of the ease of sale of the products of the chemical industry, in particular of the pharmaceutical industry, and of certain agricultural products , are absolutely necessary on the world market, since extraordinary development is possible by means of intensive processes which are well adjustable and can be carried out in an appropriate manner.

 To be able to satisfy the opposite points of view, the development of such a process or installation is desired, which with a low investment expenditure, and with a transformation of a small order of magnitude, of the current operating technologies, but working with a high degree of efficiency, allows maximum energy savings and at the same time meets current quality requirements.

In the above-mentioned branches of the chemical and allied industries, the most common installations are receptacles fitted with an envelope for heat transfer, mounted with an agitator, i.e. autoclaves having a capacity of 0.05 m3 to 10 m3. The greatest advantage of these installations also lies in their simple operation and their general character, since the installations mentioned can be used in an almost universal way for carrying out the processes which are linked to the transfer of heat and material or with transformations. chemicals. The popularity of these installations is also attributed to this fact because the simplicity and the absence of conditions represent in each case favorable properties and must be considered in the future as favorable characteristics. Unfortunately, this solutiontmeme with the advantageous properties mentioned, is not economical and is not suitable for carrying out specific procedures. The causes are as follows: compared to its volume, the heat transmitting surface is small. While a so-called "duplicator" device with a capacity of 0.05 m3 has a heat transmission surface of 0.38 m2, or else a specific heat transmission surface of 7.6 m2 / m3, a surface of heat transmission of only 0.8 m2, i.e. a specific value of 5.3 m2 / m3, can be adapted to a capacity of 0.15 m3. With increasing capacity, the specific surface decreases. Since these installations are equipped with a rotating agitator itself with a low speed, a powerful mechanical mixing is limited by technical factors, the movement of the solution is not satisfactory in any way, and therefore the distribution of heat is not even uniform. As a result, the heat and material transmission processes take place with a low degree of efficiency, and therefore it is not possible, given the construction of the installation, to intervene quickly and efficiently during the operation. In order to illustrate this problem concretely, here are two examples
- For a crystallization carried out by cooling, the side layer in the vicinity of the cold surface is the most cooled because in this place, the elimination of heat is the most intense. This results in the formation of a crust, it is that is to say, a deposit of crystals taking place on the cold surface in an almost inevitable way, so that the transfer of heat, however slight, becomes bad in increasing proportions. Furthermore, a crystallization satisfying current conditions can only be obtained by orienting and controlling the kinetic process and only by carrying out an intensive and adjustable contact. Only, in this case, a product having a regular size and grain quality1 can be produced. In order to be able to achieve the intended goal, the programmed change in the temperature of the solution and the concentration as a function of a displayed speed is inevitable. It is obvious that in this case, the autoclave equipped with a stirrer does not exhibit the more the solution the better.

 - It is a well known fact that chemical reactions take place in homogeneous or heterogeneous phases, at a given temperature, and at a given speed. In most cases, the reactions generate heat, that is, they are exothermic. It is particularly important to quickly and accurately remove the reaction heat formed, otherwise other unwanted, possibly dangerous reactions may occur. It is even understandable that in the solution too much local cooling or heating should be avoided. For a perfect progress each time of the intended reaction, the intensive mutual contact of the phases entering in reaction, and the evacuation of the product must be ensured. However, autoclaves are still used today as reactors in a wide area. We seek to avoid the difficulties mentioned by mounting a cascade of reactors constituting several low capacity units, which means that this solution consumes a lot of energy.

 The use of the process according to the present invention offers the possibility of keeping the autoclaves which are commercially available or which are already in operation as the most expensive elements of the installation. In this process, the heating or cooling of the envelope is used as a possibility of balancing the temperature, the actual heat exchange takes place outside the container in a circulation cycle which performs a intensive and satisfactory thermal inertia. At the same time, thanks to an advantageously dimensioned interior accessory element acting in a special way, efficient mixing and mutual contact of the phases are obtained in the container.

 The principle of the process according to the present invention and the way of acting of the special interior accessory element are explained by the description of an installation mounted for general cases, represented schematically on the drawing of the attached single figure. .

 A container 2, equipped with an envelope 1 for balancing the temperature, is used to collect the liquids participating in the liquid-liquid or liquid-solid phase process, and here the mutual contact and the reactions are accelerated. When two separate phases are present, the higher density phase is found in part A of the container 2. The equilibrium of the temperature of the container 2 is carried out by means of the pipes 3.

 If then, the process is started, the pump 6 sends under pressure the liquid sucked by the suction pipe 10 through the heat exchanger 7 oh the heat exchanger medium penetrating through the pipes 9, cools or heats the liquid at the temperature necessary for the process. The column of liquid arriving with a predetermined speed reaches the interior accessory element 8 and expels the air present in this element 8, but only to such an extent that in the T-shaped part 12 of the accessory element 8 which is swollen, and which is dimensioned in accordance with the given process, the air bubble 11, or a layer of gas, are maintained for the entire duration of the process, while the liquid on the inner wall of the swollen part 12 the accessory element 8 arrives with a modified speed in the form of a film layer in the interfacial layer 13.

 If necessary, by operating the valve 5, the nature of the gas layer 11 can be changed by the introduction of an inert gas from the outside. If necessary, the volume of the gas layer 11 can be modified by operating the valve 5. In the interfacial layer 13, proportional values in temperature and in almost constant concentration, or modifying according to a given function, of the components arriving in this layer from above and below, allow to intensify and guide the desired process. The continuous renewal of the interfacial layer 13 is obtained by the continuous elastic movement of the gas layer 11 and by the kinetic energy of the film of liquid forming on the interior wall of the swollen portion 12 of the interior accessory element 8 As a result of this common action, an outwardly directed flow of liquid is established from the interfacial layer 13, which is capable of causing regular mixing or, in the presence of granular materials, separation in all the recipient. Mixing is sufficient so that in the procedures carried out in a solid liquid, dissolution or crystallization phase, the grains are kept continuously in motion, which means that favorable conditions are created for the course of the material transfer process, or else for that the effective contact between the liquid phases which do not mix with each other is achieved in chemical reactions in heterogeneous phase during a liquid-liquid extraction.

 The product obtained can be removed from the container 2 by the tubing 4.

An exemplary embodiment for a dissolution is as follows
Once the liquid phase and the solid phase have arrived in the container 2, the process is started by starting the pump 6 and forming the gas layer 11.

By effect of the difference existing in the specific weights, the more or less delimitable parts A and B are formed which are different in their solid matter content, and from these parts, part A is already generally enriched in solid matter, c ie in crystals to dissolve. The solvent sucked in from part B via the tubing 10 with the pump 6, heats up in the heat exchanger 7 and
arrives accelerated on the inner wall of the swollen part 12
of the interior accessory element 8 in the interfacial layer
13 intensely agitated by the gas layer 11 and enriched
in solid matter, where saturation occurs. The process is continued until the solid phase is completely dissolved.

An exemplary embodiment for crystallization is the
following.

After the saturated solution arrives in the container
2, the starting of the pump 6 and the formation of the gas layer 11, the stream of liquid sucked through the pipe 10 cools in the heat exchanger 7; depending on the operating parameters chosen, the stream of cooled liquid arrives in the form of a film on the inner wall of the swollen part 12, with a speed determined by the speed of the pump, in the interfacial layer 13, vigorously mixed by the gas layer 11 and the kinetic energy of the film formed, where the growth of the crystals takes place up to a value determined by the proportional values of temperature and concentration.

 The size of the crystals being formed can be influenced by the temperature and current parameters. The crystals formed leaving the interfacial layer 13, or their direct environment, undergo a certain separation in which the denser suspension containing the large grains is in part A, while in part B is maintained the light phase which contains the small grains which do not settle for a current speed established by the circulation pump for the container. In this way, by adjusting the level of the suction tube 10, the lower limit of the grain size zone of the crystal aggregates can be influenced, since the small grains absorbed increase in the repeated process.

 As far as saving time is concerned, this is not yet discussed here, since the authors of the present invention have also sought to achieve carefully chosen, slow and controlled cooling. However, the quality of a calcium chloride product obtained in a traditional "Duplicator" can be compared with each of the products prepared according to the new process.

 In a "Duplicator", a product with a heterogeneous particle size is obtained. The grain size varies between 0.02 mm and 0.3 mm, the average size is 0.1 mm. The grains have an irregularly developed lamellar structure.

 In the new process, energetic mixing and directed crystal growth have grains having a cubic structure, isometric in all directions. The grain size varies between 0.1 and 0.25 mm, the average size is 0.16 mm. The particle size is much more homogeneous.

An exemplary embodiment for dissolution is as follows
The method according to the present invention is compared with the conventional method carried out in a duplicator "mounted with an agitator.

 A solution of potassium chloride saturated at 600 is prepared, and indeed so that 450 g of solid salt and 1 liter of water at 200C, or its multiple, fill a laboratory apparatus. Soon the solvent heats up, the dissolution occurs continuously and when the temperature of 600C is reached, the total amount of solid matter is dissolved. It is assumed that in the two devices there is the same amount of solution, for example 4 liters and 4 liters. A heat transfer surface of 0.1 m2 (split part) belongs to the "Duplicator having a volume of 4 liters. The container for dissolution forming the object of the present invention also has a capacity of 4 liters, which means that the The tubular heat exchanger belonging to it, located in the external circuit, has an area of 0.05 m2. In a conventional "Duplicator", 4 liters of saturated 600C solution with vigorous mechanical stirring, are finished in 30 minutes. a heating medium of the same temperature and for the same quantity, this duration is only 20 minutes in the new installation. The saving of time is attributed to the good mixing ratios prevailing in the installation and to the powerful thermal contribution caused It is clearly visible that in the process according to the present invention, the heat supply surface is purely and simply equal to half the surface of traditional installations. However, the time required for the process to proceed can be shortened in particular.

 Thanks to the analogous use of the embodiments shown, other processes developing in homogeneous or heterogeneous liquid phase, such as for example extraction, chemical reactions, etc., can be carried out.

The diffuser-mixer according to the present invention and the process carried out with this diffuser have many advantages, namely
- Intense and continuous reactions can be carried out in simple and traditional jacketed reactors #;
- Engineering in the chemical industry spares a high risk caused by the increase in scale, because the current and contact ratios can be maintained at the same value and adjusted outside the reactor.

 Maintenance can be carried out practically as a whole outside the reactor, because in the reactor, neither deposition nor engorgement occurs.

 In a traditional batch reactor, long operation can be maintained with an appropriate number of heat exchangers connected in parallel.

Claims (2)

 1. Diffuser-mixer for a reactor, characterized in that it has the shape of a hollow body (8) developing from top to bottom with an open lower end, that it is provided with one or more openings (5) introducing the reaction medium (s) and includes a lower flange (12) plunging into the liquid medium of the reactor.  2. Method of using the diffuser-mixer according to claim 1, in a reactor, characterized in that  - the heat transfer of the desired reaction is carried out with an optimal value outside the reactor by heat exchange,  the maintenance of the reaction heat is optionally carried out by means of a heat exchange occurring inside the reactor,  - and mutual contact between the reacting media is obtained so that inside the static diffuser-mixer, immersed in one of the liquid media in the reactor, a film layer is formed with the other liquid introduced using a gas layer (11) maintaining equilibrium; moreover in the interfacial layer (13) of the gas layer, of the film of liquid, as well as of the level of the liquid, an intense mixing is carried out between the surfaces of the pulsed materials and the surfaces of the renewing materials.